Polishing processes for shallow trench isolation substrates

ABSTRACT

Methods and compositions are provided for planarizing a substrate surface with reduced or minimal topographical defect formation during a polishing process for dielectric materials. In one aspect a method is provided for polishing a substrate containing two or more dielectric layers, such as silicon oxide, silicon nitride, silicon oxynitride, with at least one processing step using a fixed-abrasive polishing article as a polishing article. The processing steps may be used to remove all, substantially all, or a portion of the one or more dielectric layers, which may include removal of the topography, the bulk dielectric, or residual dielectric material of a dielectric layer in two or more steps.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of U.S. provisional patentapplication serial No. 60/421,444, filed Oct. 25, 2002, which is hereinincorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates generally to the fabrication ofsemiconductor devices and to polishing and planarizing of substrates.

[0004] 2. Description of the Related Art

[0005] Reliably producing sub-half micron and smaller features is one ofthe key technologies for the next generation of very large-scaleintegration (VLSI) and ultra large-scale integration (ULSI) ofsemiconductor devices. However, the shrinking dimensions ofinterconnects in VLSI and ULSI technology has placed additional demandson the processing capabilities. The multilevel interconnects that lie atthe heart of this technology require precise processing of high aspectratio features, such as vias, contacts, lines, and other interconnects.Reliable formation of these interconnects is important to VLSI and ULSIsuccess and to the continued effort to increase circuit density andquality of individual substrates and die.

[0006] Multilevel interconnects are formed by the sequential depositionand removal of materials from the substrate surface to form featurestherein. As layers of materials are sequentially deposited and removed,the uppermost surface of the substrate may become non-planar across itssurface and require planarization prior to further processing.Planarizing a surface, or “polishing” a surface, is a process wherematerial is removed from the surface of the substrate to form agenerally even, planar surface. Planarization is useful in removingexcess deposited material and in removing undesired surface topographyand surface defects, such as rough surfaces, agglomerated materials,crystal lattice damage, scratches, and contaminated layers or materialsto provide an even surface for subsequent processing.

[0007] Chemical mechanical planarization, or chemical mechanicalpolishing (CMP), is a common technique used to planarize substrates. Inconventional CMP techniques, a substrate carrier or polishing head ismounted on a carrier assembly and positioned in contact with a polishingmedia in a CMP apparatus. The carrier assembly provides a controllablepressure to the substrate urging the substrate against the polishingmedia. The substrate and polishing media are moved in a relative motionto one another.

[0008] A polishing composition is provided to the polishing media toeffect chemical activity in removing material from the substratesurface. The polishing composition may contain abrasive material toenhance the mechanical activity between the substrate and polishingmedia. Thus, the CMP apparatus effects polishing or rubbing movementbetween the surface of the substrate and the polishing media whiledispersing a polishing composition to effect both chemical activity andmechanical activity. The chemical and mechanical activity removes excessdeposited materials as well as planarizing a substrate surface.

[0009] Chemical mechanical polishing may be used in the fabrication ofshallow trench isolation (STI) structures. STI structures may be used toseparate transistors and components of a transistor, such assource/drain junctions or channel stops, on a substrate surface duringfabrication. STI structures can be formed by depositing a series ofdielectric materials and polishing the substrate surface to removeexcess or undesired dielectric materials. An example of a STI structureincludes depositing a silicon nitride layer on an oxide layer formed ona silicon substrate surface, patterning and etching the substratesurface to form a feature definition, depositing a silicon oxide fill ofthe feature definitions, and polishing the substrate surface to removeexcess silicon oxide to form a feature. The silicon nitride layer mayperform as a barrier layer, a hard mask during etching of the featuresin the substrate and/or as a polishing stop during subsequent polishingprocesses. Such STI fabrication processes require polishing the siliconoxide layer to the silicon nitride layer with a minimal amount ofsilicon nitride removed during the polishing process in order to preventdamaging of the underlying materials, such as oxide and silicon.

[0010] The STI substrate is typically polished using conventional,abrasive-free, polishing media and an abrasive containing polishingslurry. However, polishing STI substrates with conventional polishingarticles and abrasive containing polishing slurries has been observed toresult in overpolishing of the substrate surface and forming recesses inthe STI features and other topographical defects such as microscratcheson the substrate surface. This phenomenon of overpolishing and formingrecesses in the STI features is referred to as dishing. Dishing ishighly undesirable because dishing of substrate features maydetrimentally affect device fabrication by causing failure of isolationof transistors and transistor components from one another resulting inshort-circuits. Additionally, overpolishing of the substrate may alsoresult in nitride loss and exposing the underlying silicon substrate todamage from polishing or chemical activity, which detrimentally affectsdevice quality and performance.

[0011] FIGS. 1A-1C are schematic diagrams illustrating the phenomena ofdishing and nitride loss. FIG. 1A shows an example of a patterned STIsubstrate with a substrate 10, having a thermal oxide layer 10 disposedthereon, a polishing/etch stop layer 20, such as silicon nitride,disposed on the thermal oxide layer 15, and patterned to have featuredefinitions 35. The feature definitions 35 are then filled with adielectric fill material 30, such as a silicon oxide material, withexcess dielectric fill material 40 formed over the feature definitions35 and silicon nitride layer 20.

[0012]FIG. 1B illustrates the phenomena of dishing observed withpolishing by conventional techniques to remove the excess dielectricfill material 40. During polishing of the silicon oxide material 30 tothe silicon nitride layer 20, the silicon oxide material 30 may beoverpolished to remove any residual dielectric fill material 30, whichmay result in surface defects, such as recesses 45, formed in thedielectric fill material 30 in the feature definitions 35. The amount ofdishing 50 from the desired amount of dielectric fill material 30 in thefeature definitions 35 is represented by dashed lines.

[0013]FIG. 1C illustrates nitride loss from the surface of the siliconnitride layer 20 from excess polishing of the substrate surface withconventional polishing processes. Silicon nitride loss may take the formof excess removal of silicon nitride, or “thinning” of the siliconnitride layer, from the desired amount 60 of silicon nitride. Siliconnitride loss may also be premature removal of the silicon nitride layerand exposing the underlying oxide layer 15 and substrate material 10.The silicon nitride loss may render the silicon nitride layer 30 unableto prevent or limit damage to or contamination of the underlyingsubstrate material during polishing or subsequent processing.

[0014] STI polishing with fixed-abrasive polishing articles have shownreduced dishing and improved polishing uniformity compared withconventional slurry polishing processes. A fixed-abrasive polishingarticle generally contains fixed-abrasive particles held in acontainment media, or binder, which provides mechanical activity to thesubstrate surface, along with a plurality of geometric abrasivecomposite elements adhered to the containment media. However,conventional fixed-abrasive polishing processes have an inherently lowremoval rate of oxide material thereby increasing polishing times andreducing substrate throughput. Increased processing time may also occurin conventional deposition processes that use excess material depositionon the substrate surface, referred to as overfill, to ensure fill offeatures formed in the substrate surface.

[0015] Several approaches have been examined for limiting the extent ofoxide overfill in forming STI features for improved processingthroughput. One approach includes using multiple deposition, for examplehigh density plasma chemical vapor deposition (HDP CVD) and etchingsteps to deposit, etch back, and re-fill substrate features. Anotherapproach uses a sputter or etching process to thin the overfilldeposited on the substrate surface. Other approaches include using apost deposition wet etch process to etch the oxide film so that there isstill topography remaining for use with fixed-abrasive polishingarticles. However, these processes have been observed to increaseintegration complexity and also have increased processing times andreduced substrate throughput.

[0016] Therefore, there exists a need for a method and polishingcomposition that facilitates the removal of dielectric materials withminimal or reduced defect formation during polishing of a substratesurface.

SUMMARY OF THE INVENTION

[0017] Aspects of the invention generally provide a method andcomposition for planarizing a substrate surface with reduced or minimaldefects in surface topography. In one aspect, a method is provided forprocessing a substrate including providing a substrate comprising afirst dielectric material disposed on a second dielectric material,polishing the substrate with a first polishing composition and aabrasive-free polishing article until bulk first dielectric material issubstantially removed, and polishing the substrate with a secondpolishing composition and a fixed-abrasive polishing article to removeresidual first dielectric material formed thereon.

[0018] In another aspect, a method is provided for processing asubstrate including providing a substrate comprising a first dielectricmaterial disposed on a second dielectric material, wherein the surfaceof the first dielectric material has a non-planar topography, polishingthe substrate with a first polishing composition and a firstfixed-abrasive polishing article to remove at least the topography ofthe first dielectric material, polishing the substrate with a secondpolishing composition and a abrasive-free polishing article until bulkfirst dielectric material is substantially removed; and polishing thesubstrate with a third polishing composition and a second fixed-abrasivepolishing article to remove residual first dielectric material formedthereon.

[0019] In another aspect, a method for processing a substrate isprovided including providing a substrate comprising a first dielectricmaterial disposed on a second dielectric material, wherein the surfaceof the first dielectric material has a non-planar topography, polishingthe substrate with a first polishing composition and a firstfixed-abrasive polishing article to remove at least the topography ofthe first dielectric material, polishing the substrate with a secondpolishing composition and a second fixed-abrasive polishing articleuntil bulk first dielectric material is substantially removed, andpolishing the substrate with a third polishing composition and a thirdfixed-abrasive polishing article to remove residual first dielectricmaterial formed thereon.

[0020] In another aspect, a method is provided for processing asubstrate including providing a substrate comprising a first dielectricmaterial disposed on a second dielectric material, wherein the surfaceof the first dielectric material has a non-planar topography, polishingthe substrate with a first polishing composition and a first polishingarticle to remove at least the topography of the first dielectricmaterial, polishing the substrate with a second polishing compositionand a second polishing article until bulk first dielectric material issubstantially removed, and polishing the substrate with anabrasive-containing polishing composition and a hard polishing articleto remove residual first dielectric material formed thereon.

[0021] In another aspect, a method is provided for processing asubstrate including providing a substrate comprising a first dielectricmaterial disposed on a second dielectric material, wherein the surfaceof the first dielectric material has a non-planar topography, polishingthe substrate with a first polishing composition and an abrasive-freepolishing article to remove at least the topography of the firstdielectric material, polishing the substrate with a second polishingcomposition and a first fixed-abrasive polishing article until bulkfirst dielectric material is substantially removed, and polishing thesubstrate with a third polishing composition and a second fixed-abrasivepolishing article to remove residual first dielectric material formedthereon.

[0022] In another aspect, a method is provided for processing asubstrate including providing a substrate comprising a first dielectricmaterial disposed on a second dielectric material, wherein the surfaceof the first dielectric material has a non-planar topography, polishingthe substrate with a first polishing composition and a fixed-abrasivepolishing article to remove at least the topography of the firstdielectric material, and polishing the substrate with a second polishingcomposition and a abrasive-free polishing article until bulk firstdielectric material is substantially removed.

[0023] In another aspect, a method is provided for processing asubstrate including providing a substrate comprising a first dielectricmaterial disposed on a second dielectric material, wherein the surfaceof the first dielectric material has a non-planar topography, polishingthe substrate with a first polishing composition and a first polishingarticle to remove at least the topography of the first dielectricmaterial, polishing the substrate with a second polishing compositionand a second polishing article until bulk first dielectric material issubstantially removed, and polishing the substrate with anabrasive-containing polishing composition and a abrasive-free polishingarticle to remove residual first dielectric material formed thereon.

[0024] In another aspect, the surface of fixed-abrasive polishingarticles may be altered or modified with a non-mechanical techniqueselected from the group of applying heat to the polishing article,chemical etching the polishing article, or combinations thereof, toincrease abrasive discharge from the fixed-abrasive polishing articleprior to or during a polishing step or process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] So that the manner in which the above recited features areattained and can be understood in detail, a more particular descriptionof the invention, briefly summarized above, may be had by reference tothe embodiments thereof which are illustrated in the appended drawings.

[0026] It is to be noted, however, that the appended drawings illustrateonly typical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

[0027] FIGS. 1A-1C are schematic diagrams illustrating the phenomena ofdishing and nitride loss;

[0028] FIGS. 2A-2C are schematic diagrams illustrating one embodiment ofa two-step polishing process;

[0029] FIGS. 3A-3D are schematic diagrams illustrating one embodiment ofa three-step polishing process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0030] In general, aspects of the invention provide compositions andmethods for planarizing a substrate surface with reduced or minimaldefects in surface topography. The invention will be described below inreference to a planarizing process for the removal of dielectricmaterial, such as silicon containing materials, from a substrate surfaceby chemical mechanical planarization, or chemical mechanical polishing(CMP) technique. Chemical mechanical polishing is broadly defined hereinas polishing a substrate by a combination of chemical and mechanicalactivity.

[0031] The planarizing processes described herein may be performed bychemical mechanical polishing processing equipment, such as theReflexion™ polishing system, the Mirra®) polishing system, and theMirra® Mesa™ polishing system, all of which are available from AppliedMaterials, Inc., of Santa Clara, Calif. The Reflexion™ polishing systemis a linear polishing system more fully described in U.S. Pat. No.6,244,935, and entitled, “Apparatus And Methods For Chemical MechanicalPolishing With An Advanceable Polishing Sheet,” the entirety of which isincorporated herein by reference to the extent not inconsistent with theinvention. The Mirra® polishing system is further described in U.S. Pat.No. 5,738,574, and entitled, “Continuous Processing System for ChemicalMechanical Polishing,” the entirety of which is incorporated herein byreference to the extent not inconsistent with the invention.

[0032] Although the processes and compositions described herein may bereferenced for use in the three platen Reflexion™ polishing system orMirraμpolishing system, any system enabling chemical mechanicalpolishing using the composition or processes described herein can beused to advantage. Examples of other suitable apparatus include orbitalpolishing systems and other linear polishing systems using a sliding orcirculating polishing belt or similar device.

[0033] Chemical Mechanical Polishing Process

[0034] Aspects of the invention provide polishing methods andcompositions to planarize a substrate surface with reduced or minimaltopographical defect formation during a polishing process for dielectricmaterials. Generally, methods are provided for polishing a substratecontaining two or more dielectric layers, such as silicon oxide, siliconnitride, silicon oxynitride, with at least one processing step using afixed-abrasive polishing article as a polishing article. The processingsteps may be used to remove all, substantially all or a portion of theone or more dielectric layers. For example, a processing step using afixed-abrasive polishing article may be used to remove the topography,the bulk dielectric, and/or residual dielectric material of a dielectriclayer.

[0035] Topography is broadly defined herein as any projections orrecessions formed at the exposed surface of a dielectric material, whichprovides a non-planar surface. For example, high density plasma (HDP)chemical vapor deposition of silicon oxide may produce an exposedsurface containing peaks of material extending above the bulk siliconoxide material. Bulk dielectric material is broadly described herein asdielectric material deposited on the substrate in an amount more thansufficient to substantially fill features formed on the substratesurface. The bulk dielectric material may also be referred to asoverfill material or blanket material. Residual dielectric material isbroadly defined as any bulk dielectric material remaining after one ormore polishing process steps as well as the residue of any additionalmaterials from layers disposed below the bulk dielectric material.Residual conductive material may partially or completely cover thesurface a substrate. For example, residual material may cover about 25%or less of the surface area of the substrate. In another example,residual material may comprise about 25% or less of the originallydeposited dielectric material, such as about 1000 Å remaining after apolishing step on 4000 Å of dielectric material.

[0036] Two-Step Polishing

[0037] A substrate may be polished in a two-step polishing process usinga fixed-abrasive polishing article for at least one of the polishingsteps.

[0038] FIGS. 2A-2C illustrate one embodiment of a two-step polishingprocess. A substrate 100 having a patterned feature definitions 135formed in a material layer 110, such as a polysilicon material or dopedpolysilicon layer, an oxide layer 115, such as silicon oxide, and apolishing/etch stop layer 120, such as a dielectric barrier or etch stopmaterial, is subjected to a bulk deposition of a dielectric fillmaterial 130 on the substrate surface in a sufficient amount to fillfeatures definitions 135. The dielectric fill material is a firstdielectric material, such as silicon oxide, and the dielectric barrieror etch stop material is a second dielectric material, such as siliconnitride.

[0039] The deposited dielectric fill material 130 generally has anexcess material deposition 145 of bulk dielectric material, that has anuneven surface topography 140 with peak and recesses typically formedover feature definitions 135 having varying widths as shown in FIG. 2A.Dielectric fill material 130 is then polished in a first polishing stepto remove the bulk of the dielectric fill material 130 over the barrierlayer 120 as shown in FIG. 2B. The remaining dielectric fill material,residual dielectric material 150, is then polished in a second polishingstep to form a planarized surface with isolated features 160 as shown inFIG. 2C.

[0040] In one embodiment of a two-step polishing process, a substratehaving a first dielectric material, such as silicon oxide, disposed on asecond dielectric material, such as silicon nitride, may be firstpolished with a first polishing composition and a abrasive-freepolishing article to remove or substantially remove the bulk of thefirst dielectric material, and then be polished with a second polishingcomposition and a fixed-abrasive polishing article to remove anyresidual first dielectric material disposed on the substrate surface.

[0041] The first polishing step involves polishing the substrate with anabrasive-containing polishing composition, for example, silica or ceriaslurry, on an abrasive-free polishing article to remove most of thetopography and the bulk first dielectric material. An example of anabrasive-free polishing article is the IC-1000 polishing articlecommercially available from Rodel Inc., of Phoenix Ariz.

[0042] For example, the substrate may be polished with a silica slurryor ceria slurry on a conventional polishing article with the polishingto remove about 80% of the dielectric fill material 130, and ending whenthere is approximately 20% of residual dielectric material 150remaining. The first polishing composition may be a non-selective or lowselectivity polishing composition. Selectivity is broadly defined hereinas the preferential removal of one material in comparison to anothermaterial and is typically denoted as a removal rate ratio between afirst material and second, or subsequent, materials.

[0043] The second polishing step may include polishing a substrate withan abrasive-free polishing composition and a fixed-abrasive polishingarticle. The fixed-abrasive polishing article may be a high removal ratefixed-abrasive web material, for example, the SWR-521 fixed-abrasivepolishing article, commercially available from 3M of Minneapolis, Minn.The abrasive-free polishing composition may be a high selectivitypolishing composition to terminate the polishing process without removalof the second dielectric material. One example of a polishingcomposition for use with fixed-abrasive polishing articles is a prolineor I-proline containing polishing composition which is more fullydescribed in co-pending U.S. patent application Ser. No. 10/074,345[Atty. Docket No. 6075/CMP/CMP/RLKK], filed on Feb. 12, 2002, andentitled “STI Polish Enhancement Using Fixed Abrasives With Amino AcidAdditives”, which is incorporated herein by reference to the extent notinconsistent with the disclosure and claimed aspects herein.

[0044] Alternatively, the two-step method may comprise a first polishingstep to remove the topography on the substrate surface by polishing thesubstrate with a first composition and a fixed-abrasive polishingarticle, and then polishing the substrate with a second polishingcomposition and an abrasive-free polishing article to remove orsubstantially remove the first dielectric material.

[0045] The fixed-abrasive polishing article may include a hard resinfixed-abrasive web, for example, SWR-159 or SWR-521, commerciallyavailable from 3M of Minneapolis, Minn. The first polishing compositionis generally an abrasive-free polishing composition and may also be alow selective or high selective polishing composition. The initialpolishing composition may also include additives, such as surfactants,to enhance removal or reduction of peaks or protuberances extendingabove the surface of the first dielectric material in order to moreeffectively remove topography.

[0046] The second polishing step involves polishing the substrate withan abrasive-containing polishing composition, for example, a silicaslurry, on a conventional, abrasive-free polishing article to remove thefirst dielectric material. The second polishing composition may be anon-selective or low selectivity polishing composition.

[0047] Three-Step Polishing

[0048] The two-step polishing processes described above may be modifiedto perform a three-step polishing process by providing an initialprocessing step to remove topography on the substrate surface prior toremoving the bulk of the dielectric material.

[0049] FIGS. 3A-3D illustrate one embodiment of a three-step polishingprocess. A substrate 200 having a patterned feature definitions 235formed in a material layer 210, such as a polysilicon material or dopedpolysilicon layer, an oxide layer 215, such as silicon oxide, and apolishing/etch stop layer 220, such as a dielectric barrier or etch stopmaterial, is subjected to a bulk deposition of a dielectric fillmaterial 230 on the substrate surface in a sufficient amount to fillfeatures definitions 235. The dielectric fill material 230 is a firstdielectric material, such as silicon oxide, and the dielectric barrieror etch stop material of the polishing/etch stop layer 220 is a seconddielectric material, such as silicon nitride.

[0050] The deposited dielectric fill material 230 generally has anexcess material deposition 245 of bulk dielectric material, that has anuneven surface topography 240 with peak and recesses typically formedover feature definitions 235 having varying widths as shown in FIG. 3A.The dielectric fill material 230 is then polished in a first polishingstep to substantially remove the topography 240 formed on the surface ofthe dielectric fill material 230 to provide a substantially planarizedsurface 255 as shown in FIG. 3B. Some topography, such as materialdeposited over large features, may have valleys that extendsubstantially into the dielectric fill material 230 and may not beremoved by the topography 240 polishing step. The dielectric fillmaterial 230 is then polished in a second polishing step to remove thebulk of the dielectric material, over the barrier layer 220 as shown inFIG. 3C. The remaining dielectric fill material, residual dielectricmaterial 250 is then polished in a third polishing step to form aplanarized surface with isolated features 260 as shown in FIG. 3D.

[0051] In one embodiment, the initial polishing step may includepolishing the substrate with an initial step polishing composition witha fixed-abrasive polishing article to remove all or substantially all ofthe topography 240. The fixed-abrasive polishing article may include ahard resin fixed-abrasive web, for example, SWR-159, commerciallyavailable from 3M of Minneapolis, Minn. The initial polishingcomposition is generally an abrasive-free polishing composition asdescribed above and may also be a low selective or high selectivepolishing composition as described herein. The initial polishingcomposition may also include additives, such as surfactants, to enhanceremoval or reduction of peaks or protuberances extending above thesurface of the first dielectric material in order to more effectivelyremove topography.

[0052] The remaining dielectric material 230 may be polished with thetwo-step polishing process described above as second and third polishingsteps of the three-step polishing process. For example, referring to thetwo-step processes described above, the second polishing step involvespolishing the substrate with a conventional abrasive-containingpolishing composition, for example, a silica slurry or a ceria slurry,on an abrasive-free polishing article to remove most of the topography240 and the bulk first dielectric material 230. For example, thesubstrate may be polished with a silica slurry or ceria slurry on aconventional polishing article with the polishing to remove about 80% ofthe dielectric fill material 130, and ending when there is approximately20% of residual dielectric material 150 remaining. The first polishingcomposition may be a non-selective or low selectivity polishingcomposition.

[0053] The third polishing step may include polishing a substrate withan abrasive-free polishing composition and a fixed-abrasive polishingarticle. The fixed-abrasive polishing article may be a high removal ratefixed-abrasive web material, for example, the SWR-521 fixed-abrasivepolishing article, commercially available from 3M of Minneapolis, Minn.The abrasive-free polishing composition may be a high selectivitypolishing composition to terminate the polishing process without removalof the second dielectric material.

[0054] In another embodiment, a three-step polishing process is used topolish the substrate surface. The first step removes the topography onthe substrate surface by polishing the substrate with a firstcomposition and a first fixed-abrasive polishing article. The firstfixed-abrasive polishing article may include a hard resin fixed-abrasiveweb, for example, SWR-159, commercially available from 3M ofMinneapolis, Minn. The first polishing composition is generally anabrasive-free polishing composition and may also be a low selective orhigh selective polishing composition. The initial polishing compositionmay also include additives, such as surfactants, to enhance removal orreduction of peaks or protuberances extending above the surface of thefirst dielectric material in order to more effectively removetopography. Alternatively, the first polishing step may be performed bypolishing the substrate with an abrasive-containing composition, such assilica or ceria slurry described herein, and an abrasive-free polishingarticle.

[0055] The second and third polishing steps may include polishing asubstrate with an abrasive-free polishing composition and afixed-abrasive polishing article to remove any remaining firstdielectric material. The fixed-abrasive polishing article for the secondand third polishing steps may be a high removal rate fixed-abrasive webmaterial, for example, the SWR-521 fixed-abrasive polishing article,commercially available from 3M of Minneapolis, Minn. The second andthird fixed-abrasive polishing articles that are used in the second andthird polishing steps may be the same or different polishing articles,but are preferably adapted or designed to deliver higher firstdielectric removal rates than the first fixed-abrasive polishing articleused in the first processing step. Multi-step polishing processes may beneeded that aggressively condition the fixed-abrasive polishing articlein the first step before removing the blanket oxide.

[0056] The first, second, and third polishing compositions may beabrasive-free or abrasive-containing polishing compositions. The first,second, and third polishing compositions may be a low selective or highselective polishing composition for improved process stability and forthe ability to end polishing on the second dielectric material.

[0057] The process steps described herein may be performed on one ormore platens, for example each separate polishing step is performed onseparate platens or multiple steps may be performed on the same platen.

[0058] Alternative Polishing Techniques

[0059] The polishing process described herein may be enhanced byadditional processing techniques. Polishing steps using fixed-abrasivepolishing articles may include a polishing composition containingabrasive particles. The presence of abrasive particles in the polishingcomposition is believed to increase the removal rate of the bulk firstdielectric material. The abrasives may be silica or ceria, which may beadded in conjunction with the first polishing composition, or may beanother polishing composition used instead of the first polishingcomposition. The abrasive-containing composition may also be a highselective slurry.

[0060] In addition, the polishing processes using fixed-abrasivepolishing articles may be modified by a non-mechanical technique toenhance erosion of the binder material containing the abrasive particlesof the fixed-abrasive polishing articles. Examples of such techniquesinclude applying energy, for example heating, to the polishing article,applying etching or reactive chemicals to the polishing articles, orcombinations thereof, to increase abrasive discharge from the bindermaterial. Techniques may be applied to increase abrasives by modifyingthe polishing conditions, such as contact pressure between the substrateand polishing article or relative rotational rates between the substrateand polishing article, or polishing compositions to increase abrasivedischarge from the binder material.

[0061] In another aspect, polishing the first dielectric layer with afixed-abrasive article to remove the topography as described herein mayfurther include conditioning the polishing article using an articleconditioning mechanism to improve polishing removal rate. A hard resinfixed-abrasive web, for example, SWR-159, commercially available from 3Mof Minneapolis, Minn., which may be used to remove the topography ismore resistant to binder erosion that other fixed-abrasive articles.Mechanical activity, such as conditioning, or other non-mechanicalactivity as described herein, may be applied to enhance erosion of thebinder material, which allows an increase in abrasives for polishing andan increase in polishing removal rate of substrate material, such as thefirst dielectric material.

[0062] The polishing article for the topography step removal may beconditioned either periodically or as necessary to increase or maintainpolishing removal rates. Conditioning of the polishing article may beperformed prior to or during all or part of the time of a polishingprocess. A high removal rate at this step is believed to removetopography, which topography can affect polishing ability of subsequentsteps, and begin removing a portion of the remaining bulk firstdielectric material. For example, if an acceptable removal rate isachieved over a series of substrate polishing, then no conditioning maybe applied, however, if the removal rate decreases, then conditioning isperformed again to increase the removal rate to the acceptable rate.Conditioning may be accomplished by a physical device like aconditioning disk or may be achieved by polishing a substrate that hastopography that is more aggressive than the actual substrates beingprocessed. In addition, the polishing article may be conditioned byadjusting processing parameters to provide the desired erosion rate ofthe binder material for the desired removal rate, for example, increasedcontact pressure between the substrate and polishing article ordecreased rotational rates of the substrate and polishing article thannormally used.

[0063] Additionally, defect formation from polishing residual materialwith a fixed-abrasive polishing article may be minimized by mechanicalactions, such as a soft-landing approach or a high speed, low pressuredechuck of the substrate from the polishing article.

[0064] Alternatively, the three polishing step processes describedherein may be modified to provide a third polishing step using anabrasive-containing polishing composition, such as silica or ceriaslurry, on a hard polishing article. A hard polishing material isbroadly described herein as a polishing material having a polishingsurface of a hardness of about 50 or greater on the Shore D Hardnessscale for polymeric materials as described and measured by the AmericanSociety for Testing and Materials (ASTM), headquartered in Philadelphia,Pa. The hard polishing article may include a polymeric material, i.e.,plastic, or foam, such as polyurethane or polyurethane mixed with afiller material, and are usually free of abrasive particles. Examples ofhard polishing articles includes the IC-1000 and IC-1010 polishingarticle from Rodel Inc., of Phoenix, Ariz.

[0065] Additionally, a polishing process using an abrasive-containingpolishing composition, such as silica or ceria slurry, on a non-abrasivepolishing article may be performed after processing steps using afixed-abrasive polishing step. This additional polishing step may beperformed after each fixed-abrasive polishing step or after the finalfixed-abrasive polishing step of a process.

[0066] The fixed-abrasive polishing article polishing enhancementprocess techniques described herein may be used to enhance other knowpolishing processes using fixed-abrasive polishing articles. Additionalsuitable processes that may be enhanced by the processes describedherein include the commonly owned polishing processes disclosed in U.S.Pat. No. 5,897,426, entitled, “Chemical Mechanical Polishing WithMultiple Polishing articles,” U.S. Pat. No. 6,435,945, entitled,“Chemical Mechanical Polishing With Multiple Polishing articles,” andU.S. Pat. No. 6,435,935, and entitled, “Chemical Mechanical PolishingProcesses and Components,” the entirety of which are incorporated hereinby reference to the extent not inconsistent with the invention.

[0067] The processes described herein are believed to effectively removethe first dielectric materials, such as oxide, with less variation anddefect formation on substrates have different pattern densities anddifferent feature sizes as well as reduce overall polishing time for aprocess and reduce polishing time of individual polishing steps that areperformed as reduced removal rates compared to conventional polishing.

[0068] Selective Polishing Compositions

[0069] The polishing steps described herein may use non-selective, lowselectivity compositions or slurries (LSS), and high selectivitycompositions or slurries (HSS) to remove dielectric material, such assilicon oxide, from the substrate surface. The low selectivitycompositions and the high selectivity compositions may be Prestonian ornon-Prestonian compositions. Prestonian compositions are broadly definedas slurries that have a removal rate proportional to both the contactpressure between the substrate and platen and the rotational speed ofthe platen. Non-Prestonian compositions have removal rates that are notproportional to the polishing pressure and the rotational speed. Forexample, a non-Prestonian composition may have a linear correlationbetween removal rate and polishing pressure, but may reach a range ofpolishing pressures, typically at decreasing polishing pressures, whichresults in no noticeable removal of material from the substrate surface.

[0070] While the following low selectivity compositions and the highselectivity compositions are described as abrasive-containingcompositions, the invention contemplates the use of abrasive-free lowselectivity compositions and the high selectivity compositions. Anexample of an abrasive free composition is described in co-pending U.S.patent application Ser. No. 10/074,345, filed on Feb. 2, 2002, (Atty.Docket No. AMAT/6075) which is incorporated by reference herein to theextent not inconsistent with the claimed aspects and disclosure herein.

[0071] Non-selective compositions generally have comparable removalrates for all materials, such as approximate removal rates of about 1:1for silicon oxide and silicon nitride. Low selectivity compositions mayhave a selectivity of silicon oxide to silicon nitride between greaterthan about 1:1 and about 5:1, such as between about 3:1 and about 4:1.Generally, the low selectivity polishing compositions include anabrasive solution, a basic compound, such as ammonia or potassiumhydroxide, and deionized water.

[0072] The low selectivity polishing compositions may include betweenabout 10 weight percent (wt. %) and about 30 wt. % of an abrasivesolution. The abrasive solutions may contain between about 10 weightpercent (wt. %) and about 30 wt. % of silica abrasive particles orbetween about 0.5 weight percent (wt. %) and about 5 wt. % of ceriaabrasive particles. An example of an abrasive particle is ceria with aparticle size of about 300 nm or less in size.

[0073] Examples of the low selectivity polishing compositions includeSS-12 (about 12 wt. % abrasive silica particles) and SS-25 (about 25 wt.% abrasive silica particles), commercially available from Cabot Corp. ofAurora, Ill. and Klebosol, from Rodel Inc., of Phoenix, Ariz.

[0074] The low selectivity composition may also be diluted prior to usein polishing processes. For example, an abrasive solution containing 5wt. % ceria may be diluted to provide about 0.2 wt. % of abrasiveparticles in the polishing composition. Another example of an abrasivesolution is HS-8005, a ceria containing slurry, commercially availablefrom Hitachi Chemical Co. Ltd., of Japan.

[0075] High selectivity polishing compositions generally have aselectivity of silicon oxide to silicon nitride of greater than about5:1, and preferably have a selectivity of about 30:1 or greater, such asbetween about 30:1 and about 50:1. The high selectivity compositions mayinclude compositions having abrasive solutions, additives, and solvent.The abrasive solutions, additives, and solvent may be a ratio of X:Y:Z,with X=1 to 20, Y=0 to 20, and Z=0 to 20. Examples of high selectivitycompositions having the ratio include 1:2.2:0, 1:11:8, 1:6:3, and1:12:7. The abrasive materials may be present in the high selectivitycomposition as described for the low selectivity compounds describedherein.

[0076] High selective polishing compositions may be formed by havingadditives combined or mixed with abrasive solutions to form the. Theadditives typically comprise compounds that suppress polishing of thesubstrate surface to control the removal rate of oxide materials.Examples of additives include surfactants, such as polycarboxylatecompounds. For example, polycarboxylate-based additives may be used toinhibit polishing and lower removal rates. An example of a suitableadditive in a solution for use with the abrasive includes 8103GPE or8102GP, commercially available from Hitachi Chemical Co. Ltd., of Japan.It is believed that additives as described herein suppress the removalrate of dielectric materials, such as silicon oxide and silicon nitride,and can be selected to selectively suppress removal of a particularmaterial, such as silicon nitride, to provide the desired selectivity.

[0077] The ratio of abrasive solutions to additives is generally betweenabout 1:1 and about 1:3, which is approximate to an abrasive solutionconcentration between about 30 volume percent (vol %) and about 50 vol %of the high selectivity polishing composition. The abrasive solutionconcentration may be considered equivalent to between about 30 weightpercent (wt. %) and about 50 wt. %. A ratio of abrasive solution toadditives of about 1:2.2 has been observed to be effective inselectively removing bulk and residual dielectric material from thesurface of a substrate.

[0078] The solvent may be any suitable solvent for a polishingcomposition, of which water, such as deionized water, is used. Thesolvent and/or additive compounds may be used to dilute the highselectivity polishing compositions to have an abrasive solutionconcentration of about 50% or less of the initial step polishingcomposition. Dilution of the abrasive solution concentration allows forfurther reducing the formation of topographical defects, such asmicroscratches, during polishing.

[0079] Substrates that may be polished by the process described hereinmay include shallow trench isolation structures formed in a series ofdielectric layers, such as silicon oxide disposed over a silicon nitridebarrier layer as shown in FIG. 1. The invention contemplates polishingdielectric materials conventionally employed in the manufacture ofsemiconductor devices, for example, silicon dioxide, silicon nitride,and silicon oxynitride. The invention also contemplates the polishing ofother dielectric materials, such as polysilicon, carbon doped siliconcarbide, phosphorus-doped silicon glass (PSG), boron-phosphorus-dopedsilicon glass (BPSG), and silicon dioxide derived from tetraethylorthosilicate (TEOS), high density plasma chemical vapor deposition(HDP-CVD) silicon oxides (HDP oxides), silane by plasma enhancedchemical vapor deposition (PECVD) can be employed, and combinationsthereof.

[0080] One example of a substrate having at least a first dielectricmaterial deposited on a second dielectric material includes the firstdielectric material of silicon oxide deposited to a thickness betweenabout 1000 Å and about 10,000 Å, such as between about 1000 Å and about6000 Å on a second dielectric material, such as silicon nitridedeposited to a thickness between about 200 Å and about 2000 Å, such asabout 1000 Å on the substrate surface. The second dielectric materialmay be deposited on an oxide layer, with the oxide layer having athickness between about 50 Å and about 200 Å, such as about 100 Å. Thebulk first dielectric material is generally removed to a thickness ofabout 500 Å over the underlying silicon nitride layer, and then a firstdielectric material residual removal process step is used to remove theremaining first dielectric material.

[0081] Polishing of the substrate surface may be performed by thepolishing conditions as follows. A contact pressure between thesubstrate and the polishing article of about 10 psi or less, such asbetween about 2 psi and about 8 psi, for example between about 3 psi andabout 5 psi, at a substrate rotational rate and polishing articlerotational rate between about 20 rpms and about 200 rpms, such asbetween about 50 rpms and about 120 rpms, for example 73 rpms for thesubstrate rotational speed and about 77 rpms for polishing articlerotational speed, for between about 30 and about 240 seconds may be usedduring polishing. The polishing compositions are delivered to thepolishing article at a flow rate of about 150 ml/min or greater.However, processing parameters such as rotational speed, duration, andpolishing pressure, will vary based upon the material used and operatorrequirements. Additionally, the above described polishing process isillustrative for use with the Mirra® Polishing system, and otherprocessing conditions for other polishing apparatus, for example theReflection™ Polishing System may be used to perform the processingdescribed herein.

[0082] Additionally, each polishing step may be followed with apolishing article and substrate rinse using deionized water. Thepolishing step may also include a finishing step of deionized waterpolish at 2 psi for 15 seconds, a second polishing composition polish at2 psi for 5 seconds, or a second polishing composition polish at 2 psifor 5 seconds followed by a deionized water polish at 2 psi for 10seconds. Further, the substrate may be cleaned by polishing thesubstrate with a soft polishing article, such as a Politex article,using deionized water, following polishing of the substrate by a highselectivity polishing process.

[0083] While the foregoing is directed to embodiments of the presentinvention, other and further embodiments of the invention may be devisedwithout, departing from the basic scope thereof, and the scope thereofis determined by the claims that follow.

What is claimed is:
 1. A method for processing a substrate, comprising:providing a substrate comprising a first dielectric material disposed ona second dielectric material; polishing the substrate with a firstpolishing composition and a abrasive-free polishing article until bulkfirst dielectric material is substantially removed; and polishing thesubstrate with a second polishing composition and a fixed-abrasivepolishing article to remove residual first dielectric material formedthereon.
 2. The method of claim 1, wherein the first polishingcomposition comprises an abrasive-containing polishing composition. 3.The method of claim 2, wherein the first polishing composition has aremoval rate ratio of first dielectric material to second dielectricmaterial of between about 1:1 and about 5:1.
 4. The method of claim 1,wherein the second polishing composition has a removal rate ratio offirst dielectric material to second dielectric material of about 30:1 orgreater.
 5. The method of claim 1, wherein the fixed-abrasive polishingarticle comprises a high removal rate fixed-abrasive web material. 6.The method of claim 1, wherein the second polishing composition furthercontains abrasive particles.
 7. The method of claim 1, furthercomprising altering the surface of the fixed-abrasive polishing articlewith a non-mechanical technique selected from the group of applying heatto the polishing article, chemical etching the polishing article, orcombinations thereof.
 8. A method for processing a substrate,comprising: providing a substrate comprising a first dielectric materialdisposed on a second dielectric material, wherein the surface of thefirst dielectric material has a non-planar topography; polishing thesubstrate with a first polishing composition and a first fixed-abrasivepolishing article to remove at least the topography of the firstdielectric material; polishing the substrate with a second polishingcomposition and a abrasive-free polishing article until bulk firstdielectric material is substantially removed; and polishing thesubstrate with a third polishing composition and a second fixed-abrasivepolishing article to remove residual first dielectric material formedthereon.
 9. The method of claim 8, wherein the second polishingcomposition comprises an abrasive-containing polishing composition. 10.The method of claim 9, wherein the second polishing composition has aremoval rate ratio of first dielectric material to second dielectricmaterial of between about 1:1 and about 5:1.
 11. The method of claim 8,wherein the first and third polishing compositions have a removal rateratio of first dielectric material to second dielectric material ofabout 30:1 or greater.
 12. The method of claim 8, wherein the firstfixed-abrasive polishing article comprises a hard resin fixed-abrasiveweb material.
 13. The method of claim 8, wherein the secondfixed-abrasive polishing article comprises a high removal ratefixed-abrasive web material.
 14. The method of claim 8, wherein thefirst and third polishing compositions further contain abrasiveparticles.
 15. The method of claim 8, further comprising altering thesurface of the first or second fixed-abrasive polishing articles with anon-mechanical technique selected from the group of applying heat to thepolishing article, chemical etching the polishing article, orcombinations thereof.
 16. A method for processing a substrate,comprising: providing a substrate comprising a first dielectric materialdisposed on a second dielectric material, wherein the surface of thefirst dielectric material has a non-planar topography; polishing thesubstrate with a first polishing composition and a first fixed-abrasivepolishing article to remove at least the topography of the firstdielectric material; polishing the substrate with a second polishingcomposition and a second fixed-abrasive polishing article until bulkfirst dielectric material is substantially removed; and polishing thesubstrate with a third polishing composition and a third fixed-abrasivepolishing article to remove residual first dielectric material formedthereon.
 17. The method of claim 16, wherein the first fixed-abrasivepolishing article has a first removal rate of the first dielectricmaterial.
 18. The method of claim 17, wherein the second fixed-abrasivepolishing article has a second removal rate greater than the firstremoval rate of the first dielectric material, and the thirdfixed-abrasive polishing article has a third removal rate greater thanthe first removal rate of the first dielectric material.
 19. The methodof claim 16, wherein the first, second, and third polishing compositionshave a removal rate ratio of first dielectric material to seconddielectric material of about 30:1 or greater.
 20. The method of claim16, further comprising conditioning the first fixed-abrasive polishingarticle prior to polishing.
 21. The method of claim 16, furthercomprising conditioning the first fixed-abrasive polishing articleduring polishing.
 22. The method of claim 16, wherein the first, second,or third polishing compositions further contain abrasive particles. 23.The method of claim 16, further comprising altering the surface of thefirst, second, or third fixed-abrasive polishing articles with anon-mechanical technique selected from the group of applying heat to thepolishing article, chemical etching the polishing article, orcombinations thereof.
 24. A method for processing a substrate,comprising: providing a substrate comprising a first dielectric materialdisposed on a second dielectric material, wherein the surface of thefirst dielectric material has a non-planar topography; polishing thesubstrate with a first polishing composition and an abrasive-freepolishing article to remove at least the topography of the firstdielectric material; polishing the substrate with a second polishingcomposition and a first fixed-abrasive polishing article until bulkfirst dielectric material is substantially removed; and polishing thesubstrate with a third polishing composition and a second fixed-abrasivepolishing article to remove residual first dielectric material formedthereon.